Friction behavior of laser cladding magnesium alloy against AISI 52100 steel

The use of magnesium alloys in engineering applications is becoming increasingly important as a relatively low density allows savings in energy consumption and therefore reduction in air pollution. An associated reduction in inertia makes these alloys potential candidates for friction components, but they suffer from poor wear resistance. Laser surface alloying with appropriate powder mixture is an innovative technique to improve surface properties of metallic alloys. In this study, the effect of laser surface alloying using Al12%Si powder on wear resistance of a magnesium alloy ZE41 is investigated. Hardness and wear resistance of the alloy are significantly enhanced after treatment

Microgeometry on surface treated part : measurement and influence

This keynote is a review of previous works on the measurement of the roughness, on the influence of roughness on the fatigue lifetime of gears, on an investigation. This presentation deals first with the development of measurement standard for three- dimensional roughness. This first work was done by A. Fabre, J. Vincenti (Arts et Métiers PArisTech, MSMP lab.) and S. Raynaud (INSA de Lyon). Using contact or non-contact facilities (contact stylus, confocal microprobe, interferometry), three-dimensional roughness is quantified by the calculation of pertinent parameters defined by the international standard EN ISO 25178-3:2010. The quantification of these specific parameters is required with a good accuracy because of the optimized design of parts. Roughness must be qualify and quantify with pertinent and sensible parameters in order to correctly define the capability and in consequence the integrity of the surface, for example in the contact zone on some mechanical parts. Previous investigations were published about the influence of measurement on particular parts [1, 2]. Contact and non-contact facilities, different conditions of measurement and different software of data treatment can influence the results. With the new international standards and the possibility to use non-contact apparatus to qualify normalized roughness, the impact of the instrumental choice on the results must be analysed. In continuity with the previous studies [1,2], in this current study, a development of a measurement standard is conducted in order to qualify roughness by different apparatus. Roughness is characterized on this new standard with confocal, and interferometric apparatus and contact apparatus. Analysis of roughness parameters is investigated in order to detect the influence of different methods of measurement. On the other hand, because of the particular shape of the standard sample developed, measurements are qualified on different zones on the standard sample. It is corresponding to different angular positions of the surface measured with the reference of measurement. This analysis is conducted in order to qualify if the incidence of the position of the measured area is quite similar using different apparatus. The second part of this presentation deals with the influence of roughness on fatigue damage : the micropitting. This second work was done by A. Fabre, L. Barrallier, M. Desvignes (Arts et Métiers ParisTech, MSMP lab.) and H.P. Evans, K. J. Sharif (Cardiff University, Tribology and Contact Mechanics Group). Micropitting is considered to be fatigue damage induced by variation of mechanical loading close to the contact zone for example on gear teeth due to surface roughness effects. In order to improve fatigue lifetime, new superficial treatment can be investigated to achieve sufficiently high yield strength or endurance, but it must be developed with the associated control of surface roughness. Some studies that have been developed in order to create a model of the effect of real initial roughness on the damage mechanism are reported on scientific literature. In our first original study [3], a generic rough profile was developed. This parametric approach was followed in order to define the main geometrical parameters that affect the fatigue lifetime. The superficial loading was given for different values of roughness parameters on one rough surface sliding against a smooth surface. In complementary to this first study, the current study is conduced in the case of meshing of two rough teeth. Seven parameters are used to describe the microgeometry of the rough surface. The method is based on the model of surface loading given by two- dimensional approach with the elasto-hydrodynamic code developed by Holmes et. al. [4]. Using the plane strain hypothesis, an analytical model is developed to assess the sub-surface mechanical loading on the rough gear teeth in the contact zone [5]. The load history is obtained for materials points beneath the surface to a depth. The Crossland criterion is used to qualify the points where fatigue damage based on quenched and tempered 32CrMoV13 material properties. Furthermore, the influence of gaseous nitriding on this steel is investigated. The prediction of fatigue life is conducted taking into account the modification of the material properties due to this thermo-chemical treatment. The third part of this presentation deals with an investigation in order to characterize the damage induced by the running-in stage. This third work was done by A. Fabre, S. Jégou, L. Barrallier (Arts et Métiers ParisTech, MSMP lab.). This study is conducted in order to complete this previous study about the influence of roughness on surface fatigue damage taking the plastic deformation due to running-in into account. Moreover the damage concerning a large volume of material is difficult to correlate directly with a global physical variable. Directly linked with the local plastification of material, damage can be described with the notification of local changes in crystallites with the increase of dislocations. The peak of X-ray diffraction is sensible to the dislocation density [6] and to the structure of dislocations.Financement sur fonds propre

Friction behavior of laser cladding magnesium alloy against AISI 52100 steel

The use of magnesium alloys in engineering applications is becoming increasingly important as a relatively low density allows savings in energy consumption and therefore reduction in air pollution. An associated reduction in inertia makes these alloys potential candidates for friction components, but they suffer from poor wear resistance. Laser surface alloying with appropriate powder mixture is an innovative technique to improve surface properties of metallic alloys. In this study, the effect of laser surface alloying using Al12%Si powder on wear resistance of a magnesium alloy ZE41 is investigated. Hardness and wear resistance of the alloy are significantly enhanced after treatment

Prediction of microgeometrical influences on micropitting fatigue damage on 32CrMoV13 steel

Dr Fabre's sabbatical period at the Cardiff School of Engineering allowed the research to be conducted. Thanks are due to the M2P department of Arts et Métiers ParisTech, to Arts et Métiers ParisTech—Aix en Provence, and to the MécaSurf laboratory for supporting the visit financially, and to Cardiff University for provision of research facilities. Dr Sharif's contribution to the research was supported financially by UK Engineering & Physical Sciences Research Council (EPSRC) with Grant no. EP/G06024X/1.Micropitting is a form of surface fatigue damage that occurs in the gear teeth. It is due to the effect of variation in the mechanical loading in the contact zone between the two teeth, induced especially by flank roughness. In this study, generic roughness profiles were built with geometrical parameters to simulate the contact between two rough surfaces. Using elastohydrodynamic lubrication code and Crossland’s fatigue criteria, the influence on fatigue lifetime was analysed for changes in each parameter. The relevant parameters were determined that influence(i) the conventional pitting,(ii) the extent to which the von Mises equivalent stress exceeds the material yield stress in the zone where micropitting occurs, and(iii) the fatigue lifetime for steel teeth. With nitriding benefits, the same trends were shown with weaker effects

Microgeometry on surface treated part : measurement and influence

This keynote is a review of previous works on the measurement of the roughness, on the influence of roughness on the fatigue lifetime of gears, on an investigation. This presentation deals first with the development of measurement standard for three- dimensional roughness. This first work was done by A. Fabre, J. Vincenti (Arts et Métiers PArisTech, MSMP lab.) and S. Raynaud (INSA de Lyon). Using contact or non-contact facilities (contact stylus, confocal microprobe, interferometry), three-dimensional roughness is quantified by the calculation of pertinent parameters defined by the international standard EN ISO 25178-3:2010. The quantification of these specific parameters is required with a good accuracy because of the optimized design of parts. Roughness must be qualify and quantify with pertinent and sensible parameters in order to correctly define the capability and in consequence the integrity of the surface, for example in the contact zone on some mechanical parts. Previous investigations were published about the influence of measurement on particular parts [1, 2]. Contact and non-contact facilities, different conditions of measurement and different software of data treatment can influence the results. With the new international standards and the possibility to use non-contact apparatus to qualify normalized roughness, the impact of the instrumental choice on the results must be analysed. In continuity with the previous studies [1,2], in this current study, a development of a measurement standard is conducted in order to qualify roughness by different apparatus. Roughness is characterized on this new standard with confocal, and interferometric apparatus and contact apparatus. Analysis of roughness parameters is investigated in order to detect the influence of different methods of measurement. On the other hand, because of the particular shape of the standard sample developed, measurements are qualified on different zones on the standard sample. It is corresponding to different angular positions of the surface measured with the reference of measurement. This analysis is conducted in order to qualify if the incidence of the position of the measured area is quite similar using different apparatus. The second part of this presentation deals with the influence of roughness on fatigue damage : the micropitting. This second work was done by A. Fabre, L. Barrallier, M. Desvignes (Arts et Métiers ParisTech, MSMP lab.) and H.P. Evans, K. J. Sharif (Cardiff University, Tribology and Contact Mechanics Group). Micropitting is considered to be fatigue damage induced by variation of mechanical loading close to the contact zone for example on gear teeth due to surface roughness effects. In order to improve fatigue lifetime, new superficial treatment can be investigated to achieve sufficiently high yield strength or endurance, but it must be developed with the associated control of surface roughness. Some studies that have been developed in order to create a model of the effect of real initial roughness on the damage mechanism are reported on scientific literature. In our first original study [3], a generic rough profile was developed. This parametric approach was followed in order to define the main geometrical parameters that affect the fatigue lifetime. The superficial loading was given for different values of roughness parameters on one rough surface sliding against a smooth surface. In complementary to this first study, the current study is conduced in the case of meshing of two rough teeth. Seven parameters are used to describe the microgeometry of the rough surface. The method is based on the model of surface loading given by two- dimensional approach with the elasto-hydrodynamic code developed by Holmes et. al. [4]. Using the plane strain hypothesis, an analytical model is developed to assess the sub-surface mechanical loading on the rough gear teeth in the contact zone [5]. The load history is obtained for materials points beneath the surface to a depth. The Crossland criterion is used to qualify the points where fatigue damage based on quenched and tempered 32CrMoV13 material properties. Furthermore, the influence of gaseous nitriding on this steel is investigated. The prediction of fatigue life is conducted taking into account the modification of the material properties due to this thermo-chemical treatment. The third part of this presentation deals with an investigation in order to characterize the damage induced by the running-in stage. This third work was done by A. Fabre, S. Jégou, L. Barrallier (Arts et Métiers ParisTech, MSMP lab.). This study is conducted in order to complete this previous study about the influence of roughness on surface fatigue damage taking the plastic deformation due to running-in into account. Moreover the damage concerning a large volume of material is difficult to correlate directly with a global physical variable. Directly linked with the local plastification of material, damage can be described with the notification of local changes in crystallites with the increase of dislocations. The peak of X-ray diffraction is sensible to the dislocation density [6] and to the structure of dislocations.Financement sur fonds propre

Characterization of oxidative stress in Leishmaniasis-infected or LPS-stimulated macrophages using electrochemical impedance spectroscopy

The physiological changes caused by external stimuli can be employed as parameters to study pathogen infection in cells and the effect of drugs. Among analytical methods, impedance is potentially useful to give insight into cellular behavior by studying morphological changes, alterations in the physiological state, production of charged or redox species without interfering with in vitro cellular metabolism and labeling. The present work describes the use of electrochemical impedances spectroscopy to simply monitor by modeling impedance plots (Nyquist diagram) in appropriate equivalent circuit, the changes affecting murine macrophage cell line (RAW 264.7) in response to parasite infection by Leishmania amazonensis or to lipopolysaccharide (LPS) treatment. These results demonstrate the ability of electrochemical impedance spectroscopy to discriminate between two opposite cell responses associated to two different stimuli, one caused by the internalization of a parasite, and the other by activation by a bacterium component. Indeed, the study has allowed the characterization, from an electrical point of view, of the extra-cellular NO radical produced endogenously and in great quantities by the inducible form of NO-synthase in the case of LPS-stimulatedmacrophages. This production was not observed in the case of Leishmania-infectedmacrophages for which to survive and multiply, the parasite itself possesses mechanisms which may interfere with NO production. In this latest case, only the intracellular production of ROS was observed. To confirm these interpretations confocal microscopy analysis using the ROS (reactive oxygen species) fluorescent probe 2′,7′-dichlorodihydrofluorescein diacetate and electron paramagnetic resonance experiments using Fe(DETC)2 as NO radical spin trap were carried out

Bonifacio – Sant’Amanza

L’occupation principale mise au jour sur le site de Sant’Amanza, lors du diagnostic réalisé sur la commune de Bonifacio, s’étale des iie-iiie s. apr. J.-C. jusqu’au xvie s. Elle est associée à deux grands types d’occupation : la mise en culture de l’espace et l’édification d’une église paléochrétienne (Sant’Amanza) jouxtée par des inhumations. Grâce à l’étude fine du mobilier céramique par Susanne Lang-Desvignes, la compréhension de l’organisation générale du vignoble a été restituée dans ses..

Animal welfare: new governance in France and european projects

The General States of 2010 were aimed at reforming the Health governance in Agriculture in France. One of the aims was, in particular to give a better definition of the notion of “health veterinarian” (habilitated or mandated). Since these, a new organization was set up. It affects in particular the settlement of new consultative committees for animal protection at the national level as well as at the regional level. In addition a project of a single “Welfare Law” is being setting up by the European institutions in the context of the other laws: Food Law and Health Law. This follows the New 2012- 2015 Animal Welfare Strategy of the European commission. This strategy would modernize and simplify the old European texts and would be inspired by the HACCP system. This new paradigm would give more responsibilities to operators. It would be based on auto controls which results would be checked at the end by official veterinarians in all Member states of the UnionDepuis les États généraux du sanitaire de 2010, destinés à réformer la gouvernance sanitaire en France et en particulier à mieux redéfinir les missions du vétérinaire sanitaire (habilité ou mandaté), une nouvelle organisation s’est mise en place concernant notamment la construction et la consultation de comités dédiés à la protection animale au niveau national et régional. Cette nouvelle organisation est explicitée dans cet article. Par ailleurs, dans le contexte général de la mise en place de « Paquets cadres » par l’Union Européenne comme le Paquet Hygiène ou le Paquet Santé « Health Law », est prévue, pour faire suite au Plan d’action 2012-2015 de la Commission européenne, une « Welfare Law ». Le but de ce projet, affiché par les instances communautaires, est de moderniser et simplifier les textes communautaires actuels concernant la protection des animaux. Pour ce faire, la Commission se base, comme dans les autres « Law » d’une obligation de résultats primant sur l’obligation et le contrôle des moyens, système inspiré des pratiques « HACCP ». Ce système octroie plus de responsabilités aux opérateurs ou professionnels. Il prévoit, entre autres, des autocontrôles dont les résultats seront à postériori contrôlés par les vétérinaires officiels (en France : inspecteurs de santé publique vétérinaires

A Thermodynamic and experimental study of low-alloy steels after carbonitriding in a low-pressure atmosphere

The effect of the composition of two steels (B and 6MnCr5) on precipitation of undesirable phases (carbides, nitrides and carbonitrides) under thermochemical treatment (low-pressure or vacuum carbonitriding) is investigated. Metallographic and x-ray diffraction studies and thermodynamic computations are performed.BMI Fours Industriels, St. Quentin Fallavier, Franc

Image transmission through a stable paraxial cavity

We study the transmission of a monochromatic "image" through a paraxial cavity. Using the formalism of self-transform functions, we show that a transverse degenerate cavity transmits the self-transform part of the image, with respect to the field transformation over one round-trip of the cavity. This formalism gives a new insight on the understanding of the behavior of a transverse degenerate cavity, complementary to the transverse mode picture. An experiment of image transmission through a hemiconfocal cavity show the interest of this approach.Comment: submitted to Phys. Rev.